Method of determining request transmission priority subject to request content and transmitting request subject to such request transmission priority in application of fieldbus communication framework

ABSTRACT

A method of determining request transmission priority subject to request content and transmitting request subject to such request transmission priority in application of Fieldbus communication framework in which the communication device determines whether the received requests have the priority subject to the respective content, and also determines whether there is any logical operation condition established, and then the communication device transmits the received external requests to the connected slave device as an ordinary request or priority request, preventing the slave device from receiving an important external request sent by the main control end or manager at a late time.

This application is a Continuation-In-Part of my patent application Ser.No. 11/687,665, filed on Mar. 18, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to request transmission methods and moreparticularly, to a method of determining request transmission prioritysubject to request content and transmitting request subject to suchrequest transmission priority in application of Fieldbus communicationframework, which determines, by means of a communication device, whetherthe content of each received external request has the priority right,and then transmits every request subject to the priority order,preventing the slave device from receiving an external request from themaster device at a late time.

2. Description of the Related Art

Following fast development of communication technology, communicationnetworks have also been well developed. LAN (Local Area Network) and WAN(Wide Area Network) are the original categories of networks categorizedsubject to their scope and scale. A LAN connects network devices over arelatively short distance. A WAN is a geographically-dispersedcollection of LANs. The Internet is the largest WAN, spanning the Earth.

Either in LAN or WAN, Ethernet has proven itself as a relativelyinexpensive, reasonably fast, and very popular LAN technology. Ethernetcables (fiber optics or twisted pair) are limited in their reach, andthese distances are insufficient to cover medium-sized and large networkinstallations. Therefore, repeaters are used in Ethernets. A repeater inEthernet networking is a device that allows multiple cables to be joinedand greater distances to be spanned. A bridge device can join anEthernet to another network of a different type, such as a wirelessnetwork. Popular types of repeater devices are Ethernet hubs, switchesand routers. By means of the combination of Ethernet cables with hubs,switches and/or routers, an Ethernet networking allows transmission orcontrol of data or instructions among different LANs, computers, and/orother devices such as surveillance systems, security systems, automationsystems, etc.

Further, there is known a network communication architecture commonlyseen in industrial control and device communication protocol or rules,i.e., Fieldbus”. Fieldbus is usually used on the industrial networksystem for real-time distributed control. Its basic configuration is tohandle management through a central control unit so that an operator canmonitor or program the whole system. The central control unit istypically linked to a middle layer of programmable logic controllers(PLCs) via a bus system. At the bottom of the control chain is thefieldbus which links the PLCs to the components which actually do thework such as sensors, electric motors, switches and contactors.Following alternation of generations, there are now a wide variety ofconcurring fieldbus standards. Some of the most widely used ones includeCAN, EtherCAT, DeviceNet, Modbus, PROFIBUS, SECS and CompuBus.

Further, Fieldbus is a new industrial digital communications networkintended to replace the existing 4-20 mA analogue signal standard. Thenetwork is a digital, bi-directional, multidrop, serial-bus,communications network used to link isolated field devices, such ascontrollers, transducers, actuators and sensors. Each field device haslow cost computing power installed in it, making each device a “smart”device. Each device will be able to execute simple functions on its ownsuch as diagnostic, control, and maintenance functions as well asproviding bi-directional communication capabilities. With these devicesnot only will the engineer be able to access the field devices, but theyare also able to communicate with other field devices for master/slavecommunication. The major advantage of the Fieldbus that is mostattractive to the end user is its reduction in capital costs. Thesavings attained by the user stem from three main areas, initialsavings, maintenance savings, and savings due to improved systemsperformance. One of the main features of the Fieldbus is its significantreduction in wiring. Only one wire is sufficient to build a Fieldbussystem with varying number of devices. The cost of installing fieldequipment in a Fieldbus system is thus significantly reduced.Installation costs are further reduced due to the fact that the Fieldbusit is a multi-drop rather than point-to-point system and the multidropnetwork can offer a great reduction in field wiring expense. The factthat the Fieldbus system is less complex than conventional bus systemsimplies that there will be less overall need for maintenance.

FIG. 3 is a schematic drawing illustrating multiple requests receivingstatus of a communication gate according to the prior art. Under theFieldbus architecture, when the master device or communication gateway Areceived multiple requests, it transmits the requests to the slavedevice B subject to the order of FIFO (first in first out), i.e., themaster device or communication gateway A handles the received requestssubject to the order of their received times, but is unable to arrangeor transmit the received requests subject to order of their importancelevel.

Because the master device or communication gate A handles receivedrequests subject to the order of FIFO (first in first out), it may beunable to transmit a request to the slave device B in time. Whencommunication traffic is low, a communication gateway A can alwayshandle all received requests in time. However, when traffic gets higher,gateway A needs much more time to handle received requests in receivedtime order. If there is an important request arrived at this time, thegateway A may unable to transmit it to the slave device B in time sincethere are too many un-handled requests received before. This couldresult in many problems. For example, in a regular industrialmanufacturing line (such as wafer plant, plastic materials plant), whena request to alter the set values of a slave device B (for example, therevolving speed of a motor) is given to the communication gateway A, anabnormal or interruption of the manufacturing line may occur if theslave device B cannot receive the accurate request in time to executethe request on accurate time, thereby resulting in paralysis or damageof the machinery of the industrial manufacturing line. Further, in abuilding control, the temperature control, emergency exit system andother control actions need to make an accurate response at the accuratetime point. If responding tactics cannot be started at the accurate timepoint, it will get no help in reducing the probability of occurrence ofdisaster and the loss resulted from the disaster.

Therefore, it is desirable to provide a method of handling requestsaccording to priority of importance.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances inview. It is therefore the main object of the present invention toprovide a method of determining request transmission priority subject torequest content and transmitting request subject to such requesttransmission priority in application of Fieldbus communicationframework.

The present invention determines, by means of a communication device,whether the content of every received external request has the priorityright. The determination is done subject the type of request, address ofthe slave device to receive, address of the register to read/write, orany other individual or combination meaningful fields of the content.After the determination has been done, let the communicationgateway/master device transmit every received request subject to thepriority order. Therefore, the main control end or manager can send therequest to the triggering system or device of an emergency facility, forexample, the auto-control system of a building, on time. Because thetriggering of a triggering system or device must be executed on timewhen necessary; therefore, the main control end or manager must send therequest to the triggering system or device on time. Sending a triggeringrequest in priority prevents the triggering system or device of theemergency facility from receiving the request at a late time. Therefore,the application of the present invention helps lower the chance ofdisaster and the loss from any disaster, and also helps evacuation ofpeople from a disaster.

It is another object of the present invention to provide a method ofdetermining request transmission priority subject to request content andtransmitting request subject to such request transmission priority inapplication of Fieldbus communication framework, which uses differentdetermination conditions, such as the number of requests on queue, theswitching of an external switch, the value detected by an externaldevice, and etc. to enable the priority right of request which itscontent corresponds with the required content of the priority request.By means of this method, the user can set the triggering condition of acontrolled device in a specific industry or technical field to satisfydifferent industrial control requirements.

It is still another object of the present invention to provide a methodof determining request transmission priority subject to request contentand transmitting request subject to such request transmission priorityin application of Fieldbus communication framework, which categorizesthe priority right into kinds or levels so that different externalrequests having a same priority level can be categorized into one samegroup. Thus, any external request that has the highest priority will notbe arranged behind an external request that has a second-highestpriority, and the user can obtain more right to control thecommunication gate and will not be constrained by the existing Fieldbuscommunication protocol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating a communication architectureaccording to the preferred embodiment of the present invention.

FIG. 2 is a priority determination flowchart according to the presentinvention.

FIG. 3 is a schematic drawing illustrating multiple requests receivingstatus of a communication gateway according to the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

From the aforesaid prior art technique, we know that Fieldbus is amaster/slave communication protocol, and the master device orcommunication gateway under the Fieldbus architecture handles requestssubject to the order of FIFO (first in first out). Therefore, allrequests are sorting subject to their received times. Normally, in onesame Fieldbus network, it is allowed that different slave devicesconnect to one communication gateway or master device. However, thereare many different communication standards compatible to Fieldbus,including CAN, EtherCAT, DeviceNet, Modbus, PROFIBUS, CompuBus and SECS.These communication standards have the common characteristics of sharedmulti-transmission channel, multi-serial channel, bi-directional andmultidrop characteristics. Under Fieldbus communication protocol, themethod of determining request transmission priority subject to requestcontent and transmitting request subject to such request transmissionpriority in application of Fieldbus communication framework, of thepresent invention is applicable to every of the aforesaid variouscommunication standards that are compatible to Fieldbus communicationprotocol. The following description uses the term of Fieldbus tosubstitute for terms of CAN, EtherCAT, DeviceNet, Modbus, PROFIBUS, SECSand CompuBus. Further, the Fieldbus used in the present specificationmeans the protocol applied to automatic control having a master/slavearchitecture, and a request, response or exception communication mode.

FIG. 1 is a schematic drawing illustrating a communication architectureaccording to the preferred embodiment of the present invention. Asillustrated, when the communication gateway 1 has a slave device 2connected thereto and when the communication gateway 1 receives from aremote control end multiple control requests (sorting to be an ordinaryrequest 12 a, an ordinary request 12, and an important request 11), thecommunication gateway 1 determines the priority of the instructions orrequests subject to their content, so that the slave device 2 canreceive the important request 11 prior to the ordinary requests 12 and12 a.

Referring to FIG. 2 and FIG. 1 again, the determination of priorityaccording to the present invention includes the steps of:

-   (100) When a request is transmitted to the communication gateway 1,    run step (101) and (102);-   (101) Determine whether the operation condition are established or    not, and then run step (103);-   (102) Determine whether the received request has a specific content    which corresponds with the required content of the priority request,    and then run step (103);-   (103) Couple all conditions which includes conditions in step (101)    and (102) subject to the user's requirement;-   (104) Determine whether the coupling conditions are established or    not, and then run step (106) when the coupling conditions are    established;-   (105) Transmit the request as an ordinary request, and end the    procedure;-   (106) Transmit the request as a priority request, and then end the    procedure.

Briefly speaking, the invention uses two or more methods to determine orcouple conditions of external requests and then see whether they are insatisfaction of the conditions required for priority. At first, in step(101), the operation conditions can be the number of requests having thespecific content in queue, switching of external switch or any logicaloperation conditions detected by an external device (such as whether ornot in proximity to a predetermined temperature or humidity). Theseconditions can be used in step (101) as judgment values for AND or OR onlogic coupling. Further, in step (102), a request having the specificcontent can be a specific type of request (for example, a request toread/write the register), the address of a specific destination slavedevice, the address of a specific register to read/write, or any otherspecific value of individual or combination meaningful fields of therequest. Therefore, based on the aforesaid determination conditions, thecommunication gateway 1 can determine whether the received externalrequests have the priority to transmit or not, and can proceed withtransmission of requests early. When an external request is determinedto be a priority request, the communication gateway 1 can send therequest into the queue of higher priority or tag this priority requestin the priority position on the original queue, or uses any other methodto transmit this request in priority so as to obtain an earliertransmission time prior to the ordinary requests 12 and 12 a. Further,during step (100), if the format of the external request is not inconformity with the format under Fieldbus communication architecture orthe format of the external request is compatible to Fieldbuscommunication architecture (for example, Ethernet), the request can beconverted into a suitable format during step (105) or step (106) beforetransmission. Therefore, the external request can be transmitted at theformat of its source or after a format conversion.

In actual practice, when too many external requests are received, thecommunication gateway 1 may be unable to sort the priority of thereceived external requests. By means of the aforesaid method of usingrequest content, the invention determines the priority of externalrequests. Therefore, the invention eliminates the problem of beingunable to sort external requests when too many external requests arereceived. Further, the invention categorizes the priority right intokinds or levels so that different external requests having a samepriority level can be categorized into one same group. Thus, anyexternal request that has the highest priority will not be arrangedbehind an external request that has a second-highest priority, and theuser can obtain more right to control the communication gateway 1 andwill not be constrained by the existing Fieldbus communication protocol.

The method of determining request transmission priority subject torequest content and transmitting request subject to such requesttransmission priority in application of Fieldbus communication frameworkas described above is simply a preferred embodiment of the presentinvention. In actual practice, the invention could be implemented on amaster device, or a communication device or repeater which is capable toreceive external requests. Further, the operation condition to becoupled subject to the user's requirement can be the number of requestshaving the specific content in queue, switching of an external switch,or the value detected by an external device (for example, specifictemperature or humidity).

For example, the technology of the present invention is applicable inthe automation control system monitoring. The structure thereincomprises a master device capable of transmitting control requests to acommunication device 1, and the communication device 1 is capable oftransmitting control requests to a field device (slave device 2). Inother words, a master device can orderly transmit a plurality of controlrequests through the communication device 1 to one or a plurality offield devices for monitoring those filed devices. In the preferredembodiment of the present invention, plurality of control requests tothe communication device 1, each received control request would bedetermined as an ordinary request or a priority request by thecommunication device 1. When the control request is determined as anordinary request, the control request would be transmitted in thefirst-in-first-out fashion (first received one would be transmittedfirst). If the control request is determined as a priority request, thecontrol request would be transmitted in priority, which means thecontrol request would be tagged in priority position of the queue or betransmitted before all queued ordinary requests. Therefore, when thecommunication device 1 receives the plurality of control requests fromthe master device in an orderly fashion, the communication device 1determinate the priority request based on at least one of the content ofthe request and the logical operational condition of the request, forinstance, the priority request should have content includes the specifictype of request and the address of the specific register to read/write.When the master device receives a fire alarm signal for overheating inthe room from a remote sensor, the master device would transmit acontrol request of sprinkling water which includes writing a specificvalue into a specific register of the field device to the communicationdevice 1. It means the content of the received control request includesthe type of request as “write” and the address of the register foractivating the fire sprinkler. Before the control request is received,there could be a plurality of requests were already queued in thecommunication device 1 for waiting to be transmitted. If user configuresthe communication device 1 that the priority request should have contentincludes the type of request as “write” and the address of the registerfor activating the fire sprinkler, the control request would bedetermined as a priority request by the communication device 1. Then,this control request would be transmitted before all queued requests(ordinary ones) or be tagged in priority position of the queue.Therefore, after fire alarm signal is received, the master device couldactivate the fire sprinkler as soon as possible. In other words, thepresent invention makes sure the user defined important/urgent requestscould always be transmitted to the target field devices as soon aspossible.

Certainly, the determination conditions of the priority requests of thecommunication device 1 can also include both the logical operationalcondition and the specific content of the requests. The specific contentof the requests can also comprise at least one specific type of request(for example, a request to read/write the register), the address of aspecific register to read/write. The specific content of the requestscan also comprise any other specific value of individual or combinationmeaningful fields of the request. The above description merelyillustrates the preferred embodiment of the present invention, and isnot intended to limit the scope of the present invention.

When compared to the prior art technology, the invention has thefollowing advantages:

1. In regular building automation applications, proximal/remote ormaster/slave concept is adopted. All events management and emergencyhandling are connected to a computer in the main control room through atransmission interface. When a situation happens, a person in the maincontrol room or the computer issues a request to an externalinput/output device to execute a specific action, for example, turningon the radiation fan when the temperature is excessively high, turningon the alarm lamp when the exit door is abnormally opened, starting theautomatic sprinkling system when the temperature surpasses apredetermined fire temperature, etc. Because the trigging time of theseactions is critical, the communication gateway 1 that is in charge oftransferring the request must transmits the request in priority. If thecommunication gateway 1 cannot handle the priority request on time dueto reception of a big number of other unimportant requests, the maincontrol end or manager may be unable to start the related emergencyfacility at the accurate time point. Therefore, by means of determiningthe priority of each received request subject to its content, theinvention prevents the communication gateway 1 from sending out animportant request 11 at a late time, enabling the important request 11to trigger the related facility at the accurate time point, andtherefore the invention can lower the chance of disaster and the lossfrom a disaster, and can also help evacuation of people from a disaster.Therefore, the invention eliminates the problem of being unable totransmit an important request on time as encountered in the prior arttechnology, which handles all external requests subject to the order offirst-in first-out.

2. According to the existing communication protocols under Fieldbusarchitecture, it is to handle external requests subject to the order offirst-in first-out. This request transmission order does not allowtransmission of an important request in priority, and may result asystem failure. In an industrial manufacturing line (for example, awafer plant or plastic materials plant), if the communication gateway 1cannot transmit a control request to the slave device 2 or the slavedevice 2 cannot execute the request from the communication gateway 1 atthe accurate time point, the manufacturing line may be interrupted or anabnormal condition may occur in the manufacturing line, therebyresulting in paralysis or damage of the machinery of the industrialmanufacturing line. Therefore, by means of determining whether theexternal request is a request having the specific content, thecommunication gateway 1 can transmit every important request to theslave device or operating end on time, preventing a delay of triggingtime.

3. By means of different determination conditions, such as the number ofrequests having the specific content on queue, the switching of anexternal switch, the value detected by an external device, and etc. tomatch with an external request having a specific content, the user canset the triggering condition of a controlled device in a specificindustry or technical field to satisfy different industrial controlrequirements, i.e., the user can satisfy different industrial controlrequirements subject to different situations.

4. Following alternation of generations, Fieldbus communicationarchitecture has become a communication standard in industrial field,and devices in conformity with Fieldbus architecture are intensivelyused to connect different industrial electronic devices. An industrialapplication of the method of determining request transmission prioritysubject to request content and transmitting request subject to suchrequest transmission priority in application of Fieldbus communicationframework does not need to add extra physical devices or elements. Whenmatching with the widely applied Fieldbus architecture, the inventioncan achieve determination of priority right after installation orsetting of the software. Therefore, the application of the inventioneliminates installation cost of any physical device.

5. The invention uses requests under Fieldbus protocol standardsdirectly, and needs not to define other special requests. Therefore, anyrequest used does not affect normal functioning of the slave device.Further, either using the Fieldbus master device or Fieldbuscommunication gateway to transmit external requests, the priority rightof every request can be calculated through the software. Therefore, theuser needs not to worry about the system operational problem that thecontrol end cannot receive the request from the communication gateway ontime and that may affect the client's confidence in the reliability ofthe product, causing the client to reject the product.

6. By means of categorizing priority right into kinds or levels, allexternal requests have a same priority level can be categorized into onesame class. Thus, any external request that has the highest prioritywill not be arranged behind an external request that has asecond-highest priority, and the user can obtain more right to controlthe communication gateway and will not be constrained by the existingFieldbus communication protocol.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications andenhancements may be made without departing from the spirit and scope ofthe invention.

1. A method of determining request transmission priority subject torequest content and transmitting request subject to such requesttransmission priority in application of Fieldbus communicationframework, comprising the steps of: (a) external requests aretransmitted from a remote control end to a communication device oneafter another; (b) the communication device determines whether thecontent of each received request has the priority right; (c) thecommunication device determines whether there is at least one logicaloperation condition established; (d) the communication device couplesthe logical operation conditions subject to the user's setting andpriority condition of the content of each received external request; (e)the communication device determines whether each received externalrequest has the priority to transmit; (f) the communication devicetransmits each external requests that does not have the priority totransmit as an ordinary requests; and (g) the communication devicetransmits each external request that has the priority to transmit as apriority request; wherein the logical operation condition includes anon/off switch function triggerable by the user.
 2. The method as claimedin claim 1, wherein the priority request transmission procedure is tosend the external request into the communication device into a queuehaving a higher priority.
 3. The method as claimed in claim 1, whereinthe priority request transmission procedure is to tag the priorityrequest in the priority position on an original queue of thecommunication device.
 4. The method as claimed in claim 1, wherein saidcommunication device categorizes the priority right into differentlevels or kinds.
 5. The method as claimed in claim 1, wherein adetermination column of said priority right can include the type ofrequest, an address of the slave device to receive the request, and anaddress of the register to read/write.
 6. The method as claimed in claim1, wherein said communication device can be a communication gate, amaster device or a repeater capable of receiving external requests. 7.The method as claimed in claim 1, wherein if said external request isdifferent from said Fieldbus communication frame, said external requestcan be converted before transit.
 8. The method as claimed in claim 1,wherein the Fieldbus communication framework is one of the framework ofCAN, EtherCAT, DeviceNet, Modbus, PROFIBUS, CompuBus and SECS protocolsfor automated control application that has a master/slave architectureand communication mode of Request, Response or Exception.